Creatine is a fuel source for the brain, says study author Michele Skelton, Ph.D., associate professor of health sciences at Stetson University in Deland, Florida. The compound is mostly found in meat, poultry, and fish, so vegans and vegetarians often miss out on it. For them, taking the supplement regularly can boost cognitive function and increase lean mass by making more phosphocreatine (which your body converts into ATP for energy) in the brain, muscles, and other organs.
Carnivores and pescetarians likely won’t get the same benefits from extra creatine because their levels are already optimal.
The bottom line:
If you’re vegan or vegetarian, ask your doctor if you need more creatine. Study participants took five grams daily and though they saw results in less than a month, Skelton notes the effects may take six to eight weeks to kick in.